It's already happening to women who are slim, average-sized , or only slightly plump by pre1990s standards: They get "joking" remarks about how they're obviously anorexic from what one freeper here called "haystack" women (gotta remember that one, it's so apt.)
You're right. I have a perfectly normal BMI of 21 and my coworkers call me Twiggy (while eating their entire restaurant lunch every day).
It happens to me every day. I'm a 5'6" woman and weigh a good healthy 125 thanks to a heart-healthy diet full of fresh fruit and veggies, lean protein, good fats and whole grains. And I'm very fit. I get crap all the time from all the "haystacks" at work. I get called anorexic and they try to get me to eat all the donuts and other garbage that gets brought into work every day. "Well at least I'll die happy!" they sneer. Obviously they've never seen anyone die a prolonged, painful, miserable and expensive death from congestive heart failure.